Halogen-cycle incandescent lamp having a platinized interior fuse

ABSTRACT

A halogen-containing single-ended electric lamp of the type used in slide projectors is provided with a platinum-coated fuse wire of nickel or Nichrome alloy which is located within the envelope and connected in series with the tungsten filament. The platinum coating is of such thickness that it protects the wire from the hot corrosive atmosphere within the operating lamp and prevents the fusible core metal from contaminating the lamp and disrupting the halogen-regenerative cycle.

' DeCaro States atent [191 [75]' Inventor: Aristide R. DeCaro, Edison,NJ.

[73] Assignee: Westinghouse Electric Corporation,

. a Pittsburgh, Pa. 9

22 Filed: Mayll, 1971 21 App1.No.:142,303

[52] US. Cl. ..313/222', 313/107, 315/74 [51] Int. (31. ..l-l0lk 1/50,l-lOlk 1/66 [58] Field of Search...' ..3l5/74, 66, 71;

[56] References Cited UNITEDSTATES PATENTS 3,211,943 10/1965 Cardwell,Jr. ..3 1 5/74 X 2,021,758 11/1935 Van Horn 268,270, 11/1882 Nichols2,859,381 11/1958 Gray et a1 3,445,713 5/1969 Cardwell, Jr. 3,431,4483/1969 English 2,883,571 4/1959 Fridri ch et a1. 3,325,665 -6/1967*Meijer et al.

3,012,167 Poole ..313/222 UX 51 Apr. 10, 1973 FOREIGN PATENTS ORAPPLICATIONS 690,662 7/1964 Canada ..3 13/222 OTHER PUBLICATIONS PrimaryExaminer-Palmer C. Demeo Attorney-A. T. Stratton, W. D. Palmer and D. S.Buleza 57 ABSTRACT -A halogen-containing single-ended electric lamp ofthe type used in slide projectors is provided with a I 6 Claims, 2Drawing Figures PATENTED APR 1 01375 FIG. I

R O T N E V N WITNENESSES Aristide R. DeCcro W QmZ A HALOGEN-CYCLEINCANDESCENT LAMP HAVING A PLATINIZED INTERIOR FUSE CROSS-REFERENCES TORELATED APPLICATIONS The present application is related to butconstitutes an improvement over the subject matter disclosed and claimedin the following copending commonly-owned U.S. applications:

Application Ser. No. 100,665 filed Dec. 22, 1970 by N. J. Rainone et al.and entitled Halogen-Cycle Incandescent Lamp Having An Improved FilamentMount Assembly; and

Application Ser. No. 28,663 filed Apr. 15, 1970 by A. R. DeCaro et al.and entitled Lamp Combination Comprising An Improved Envelope ForTungsten- Halogen Incandescible Projection Lamp, now U.S. Pat. No.3,648,094.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to electric lamps and has particular reference to an improvedhalogen-cycle incandescent lamp of the type used in film projectors andsimilar apparatus.

2. Description of the Prior Art Incandescent lamps having built-in fuseelements that are located within the lamp envelope are per se well knownin the art. A conventional projection type lamp having such an integralfuse is disclosed in U.S. Pat. No. 2,859,381 issued Nov. 4, 1958 to S.M. Gray et al. Since such conventional projection lamps are filled withan inert gas such as nitrogen or the like, the fuse can be fabricatedfrom any metal that meets the current-carrying requirements and has theproper rigidity and melting point to fulfill the automatic fusingfunction.

The situation in the case of the so-called regenerative typeincandescent lamps is, however, quite different in that such lampscontain a highly-corrosive halogen atmosphere and operate at much highertemperatures in order to sustain the halogen-tungsten cycle whichreturns vaporized tungsten back to the filament. (This principle is wellknown and is described in detail in U.S. Pat. No. 2,883,571.) Testsconducted with fusible elements composed of bare copper, nickel, orNichrome alloy wires have shown that they are not only chemicallyattacked bythe bromine or other halogen gas used in the lamp but thatthe wires, when heated to the high temperatures which prevail within theoperating lamp, released gaseous and other impurities which contaminatedthe lamp atmosphere. This, in turn, disrupted the halogen-tungsten cycleand formed discoloring deposits on the lamp envelope which drasticallyreduced the light output.

A double-ended compact infrared heating lamp having a silica envelopeand a seal-structure wherein the portions of the lead-in conductors thatextend from the press seals formed at the ends of the envelope and areexposed tothe air are composed of platinum-sheathed tungsten orplatinum-sheathed molybednum is described in U.S. Pat. No. 3,012,167issued Dec. 5, 196] to F. E. Poole. 1

SUMMARY OF THE INVENTION 7 layer of platinum is such that it protectsthe fuse from the hot halogen atmosphere within the lamp and preventsthe nickel or Nichrome core portion of the fuse from releasingcontaminants which disrupt the halogen-tungsten cycle. The improved lampthus operates in the normal fashion and the fuse remains intact untilsuch time that the filament fails and the resulting surge in currentcauses the fuse to melt and open the circuit.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of the inventionwill be obtained from the following description of the exemplaryembodiment shown in the accompanying drawing, wherein:

FIG. 1 is a side elevational view of a halogen-cycle incandescentprojection lamp having an internal fuse structure according to theinvention; and

FIG. 2 is a cross-sectional view through the based end of the lamp,taken along line II--II of FIG. 1, showing the physical arrangement ofthe fuse assembly and the sealed-in pin members.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown arepresentative 500 watt halogen-cycle type projection lamp 10 having alighttransmitting tubular envelope 12 that is sealed by an end wallformed by fusing a disk or wafer 14 to the rim of the envelope in theusual manner. Four rigid metal pins l5, l6, l7 and 18 (see FIG. 2) arehermetically sealed through the wafer 14 and spaced equal distances fromeach other around the circumference of the wafer. A concentrated lightsource such as a planar tungsten filament 20 having a plurality ofinterconnected coil sections arranged in monoplane or biplanerelationship is suspended within the envelope 12 by a mountassemblyconsisting of a pair of support wires 22, 24 that are held inspaced-apart relation by a pair of non-conductive bridges 26 and 28. Thesupports 22, 24 are terminated by helical-coiled segments 23 and 25,respectively, that are slipped over and fastened as by spot welding tooppositely disposed pins 15 and 17, as shown. The planar filament 20 iselectrically connected to the support wires 22, 24 by short end coils 21that are spot welded in telescoped relation with slip coils force-fittedover the support wires. Hooked filamentsupport wires 27 and 29 areanchored in the top and bottom bridges 26 and 28, respectively, andcoupled to the uncoiled segments of the filament 20 that join the coilsections. A detailed description of the mount assembly and the manner inwhich it is fabricated is disclosed in the aforementioned copendingapplication of v The envelope 12 and wafer 14 are composed of quartz ora suitable high-silica content glas's (such as Pyrex" borosilicate glassNo. 7740 marketed by the Corning Glass Works) and the envelope containsa mixture of a halogen and an inert fill gas a mixture of bromine andnitrogen at a pressure of about 1,000 torrs for example. The bridgemembers 26 and 28 are composed of quartz and all of the metal parts ofthe mount assembly enclosed within the envelope 12 are composed oftungsten.

A suitable base member such as a metal shell 30 having a keyed post 31is fastened to the neck of the envelope 12 by a suitable cement 32 inthe usual manner.

In accordance with the present invention, a fuse 34 consisting of eithera platinum-plated nickel wire or a platinum-plated Nichrome alloy wireis attached to one of the auxiliary conductors and an adjacent mainconductor (pins 16 and 17 in the lamp illustrated in the drawing). Thefuse wire 34 is fastened, as by spot welding, to the inner ends of thepins 16, 17 at locations adjacent to but spaced from the envelope endwall 14. The fuse 34 is thus connected in series with the filament 20 bypins 16 and 17 which it bridges. The outer ends of pins and 16accordingly constitute exposed longitudinally-extending terminals forthe lamp 10.

A protective sleeve such as a loose-fitting glass tube 36 is desirablyplaced over the fuse wire 34 to guard against the possibility thatmolten metal from the activated fuse will strike the envelope walls andcause them to crack when the lamp fails. As will be noted in FIG. 2, theglass tube 36 is locked in such position by the connected segments ofpins 16,17.

In the case of the 500 watt T10 projection lamp 10 lllustrated having abiplane filament designed to operate at a voltage within a range of from1 10 to 130 volts, satisfactory results have been obtained by spacingthe pins 16 and 17 approximately 11 millimeters apart and using aplatinized Nichrome wire 16 millimeters long and approximately 0.4millimeters in diameter as the fuse 34. The platinum coating or sheathwas of such thickness that it protected the Nichrome core from thehalogen gas without interfering with the fusing action. Excellentresults have been obtained by employing Nichrome wire having a platinumsheath such that the platinum comprises approximately 62 percent byweight of the wire. The thickness of the platinum coating can vary andNichrome wires wherein the platinum comprises from about 30 to 70percent by weight of the wire can be used.

Nichrome" is the trade name for a series of nickelbased alloys (made bythe Driver-Harris Company) which melt at approximately l,350C. andcontain from 11 to 22 percent chromium, smaller amounts of silicon ormanganese, and optionally some iron. Such alloys are well known in theart and are used extensively as electric-resistance heating elements. Aspecific example of a suitable Nichrome alloy is one which contains 75percent nickel, l2 percent iron, ll percent chromium and 2 percentmanganese.

Since nickel has only a slightly higher melting point (1,450C) thanNichrome alloy, the same fusing action can also be obtained by using aplatinum-coated nickel wire of the same dimensions in place of theabovedescribed platinized Nichrome wire fuse element.

While the fuse 34 as illustrated in the drawing and described is aplatinum-clad wire of substantially uniform diameter, a compositemulti-section wire which has a medial segment of reduced thickness thatis composed of platinized nickel or a platinized Nichrome alloy andserves as the fusible member can also be employed. In any event, theopening in the electrical circuit formed when the fuse melts is greaterthan the maximum arcing distance for the operating voltage of thefilament that is, the gap produced within the lamp envelope by themelted fuse wire when the filament fails is too large to support an arcin the halogencontaining atmosphere of the lamp.

I claim as my invention:

1. In a regenerative-type incandescent lamp having a sealedlight-transmitting envelope that encloses a coiled tungsten filament anda halogen-containing atmosphere, the improvement comprising a fusecomponent that is connected in series with said filament, is locatedwithin said envelope, and is composed of a material selected from thegroup consisting of platinized nickel and a platinized nickel-chromiumalloy that contains less than 1 1 percent silicon or manganese.

2. The improvement of claim 1 wherein;

said filament is connected to a pair of elongated rigid main conductorsthat are embedded in an end wall of said envelope,

- a rigid auxiliary conductor is anchored in said envelope end wall andspaced from each of said main conductors,

said fuse component is connected to said auxiliary conductor and one ofsaid main conductors,

said auxiliary conductor and said one main conductor extend through theend wall of the envelope and thereby constitute a pair of exposedterminals for the lamp, and

the interior portions of said main and auxiliary conductors are composedof tungsten.

3. The improvement set forth in claim 1 wherein platinum comprises fromabout 30 to percent by weight of the fuse component.

4. The improvement set forth in claim 2 wherein;

said lamp comprises a single-ended projection lamp,

said tungsten filament comprises a planar array of interconnected coilsections,

said main and auxiliary conductors each comprise a tungsten pin, and

said fuse component comprises a wire of predetermined and substantiallyuniform diameter.

5. The projection lamp of claim 4 wherein;

said envelope is composed of borosilicate glass and contains a mixtureof an inert gas and bromine, and

each of said tungsten pins extend through the end all of said envelope.

6. The projection lamp of claim 4 wherein;

said envelope is of tubular configuration and contains a mixture ofnitrogen and bromine,

said fuse component comprises a platinum-plated wire of saidnickel-chromium alloy wherein platinum constitutes approximately 62percent by weight of the wire, and

a loose-fitting glass tube is disposed in sleeved-protectiverelationship with the fuse wire and is retained in such position by theconnected portions of the associated pins.

2. The improvement of claim 1 wherein; said filament is connected to apair of elongated rigid main conductors that are embedded in an end wallof said envelope, a rigid auxiliary conductor is anchored in saidenvelope end wall and spaced from each of said main conductors, saidfuse component is connected to said auxiliary conductor and one of saidmain conductors, said auxiliary conductor and said one main conductorextend through the end wall of the envelope and thereby constitute apair of exposed terminals for the lamp, and the interior portions ofsaid main and auxiliary conductors are composed of tungsten.
 3. Theimprovement set forth in claim 1 wherein platinum comprises from about30 to 70 percent by weight of the fuse component.
 4. The improvement setforth in claim 2 wherein; said lamp comprises a single-ended projectionlamp, said tungsten filament comprises a planar array of interconnectedcoil sections, said main and auxiliary conductors each comprise atungsten pin, and said fuse component comprises a wire of predeterminedand substantially uniform diameter.
 5. The projection lamp of claim 4wherein; said envelope is composed of borosilicate glass and contains amixture of an inert gas and bromine, and each of said tungsten pinsextend through the end all of said envelope.
 6. The projection lamp ofclaim 4 wherein; said envelope is of tubular configuration and containsa mixture of nitrogen and bromine, said fuse component comprises aplatinum-plated wire of said nickel-chromium alloy wherein platinumconstitutes approximately 62 percent by weight of the wire, and aloose-fitting glass tube is disposed in sleeved-protective relationshipwith the fuse wire and is retained in such position by the connectedportions of the associated pins.